The present disclosure relates to an image reading apparatus having a pressing member for pressing a document, and an image forming apparatus including the image reading apparatus.
Conventionally, an image reading apparatus is known which reads a document and generates image data of the document. The image reading apparatus is mounted on an image forming apparatus such as a multifunction peripheral, for example. The image reading apparatus includes a placement member for placing a document thereon, a light source for radiating light to the document, a line sensor for performing photoelectric conversion of light reflected from the document and accumulating electric charge, and the like. Generally, on the placement member, a pressing member for pressing a document is attached so as to be openable and closable with respect to the placement member.
Such an image reading apparatus detects the size of the document placed on the placement member prior to reading of the document. Here, when the size detection of the document is performed, if the pressing member is fully opened, a large amount of the light from the light source leaks out, so that a user is dazzled, thus causing inconvenience. On the other hand, if the pressing member is fully closed, in the case where a white mat is provided on a pressing surface of the pressing member, the boundary between a portion where the document is present and a portion where the document is not present cannot be read accurately.
Therefore, in the conventional image reading apparatus, the placement member is provided with an open/close detection mechanism for detecting an open/close state (an inclination angle of the pressing member) of the pressing member.
The conventional open/close detection mechanism is composed of a movable portion (actuator) which moves in an up-down direction in accordance with opening or closing of the pressing member, a guide hole (through hole) for guiding movement in the up-down direction of the movable portion, a transmission type light sensor for detecting the position in the up-down direction of the movable portion, and the like. Each placement position of the movable portion and the light sensor is adjusted such that, when the inclination angle of the pressing member becomes a predetermined angle, a portion to be detected (a portion to be detected by the sensor) of the movable portion shields a detection area (a light path between a light emitting portion and a light receiving portion) of the light sensor.
In addition, in the conventional open/close detection mechanism, the movable portion is inserted into the guide hole, whereby the movable portion is held so as not to incline. That is, the movable portion slides in the up-down direction in contact with the inner circumferential surface of the guide hole. Thus, the movement direction of the movable portion can be defined to be a desired direction (up-down direction).
However, in the conventional open/close detection mechanism, the movable portion is not reliably held. Specifically, in the open/close detection mechanism of the conventional image reading apparatus, the movable portion may rotate about the central axis thereof. If the movable portion thus rotates, a movement route in the up-down direction of the portion to be detected of the movable portion deviates from the detection area of the light sensor, thus causing inconvenience. In this case, even if the inclination angle of the pressing member has become a predetermined angle, the portion to be detected of the movable portion does not shield the detection area of the light sensor.